1. Field of the Invention
This invention relates to containers having self-locking closures formed by flaps with corners tucked under or overlapping adjacent flaps.
2. Description of the Prior Art
One prior art closure in a regular slotted container of corrugated paperboard includes four trapezoidal closure flaps hinged at the longest of their respective two parallel edges to the top edges of the walls of the container. Each of the closure flaps has one side edge, i.e. one of the non-parallel edges, perpendicular to the parallel edges, and has the other side edge formed at a 45.degree. angle to the longest parallel edge. The closure flaps are folded sequentially with a portion of each closure flap adjacent the 45.degree. angled edge overlapping a portion or corner adjacent the perpendicular edge of the previously folded flap. One of the flaps, i.e., the last flap to be closed, has a slot extending from its perpendicular side edge about one fifth of the distance along its longest parallel edge in line with the scoreline joining such flap to the container together with a scoreline extending from the inside end of the slot at a 45.degree. angle across the flap to the 45.degree. angled edge of the flap. This slot and 45.degree. score line permits the corner portion adjacent the perpendicular side edge of this last flap to be resiliently folded down and inserted into the containers under the 45.degree. angled edge of the adjacent flap to complete the closure so that the flaps are locked together. However, it is difficult to use this type of closure when the container is full of non-compressible materials since the non-compressible materials prevent the fold-down corner portion from being inserted into the container sufficiently to make the proper closure. Also distortion or deformation of the flap portion being tucked under the adjacent flap often occurs rendering the container less suitable for further use.